ORIENTATIONAL DECAY IN POLED 2ND-ORDER NONLINEAR-OPTICAL GUEST-HOST POLYMERS - TEMPERATURE-DEPENDENCE AND EFFECTS OF POLING GEOMETRY

The orientational decay of chemically and thermally stable high-temper ature chromophores doped into thin films made from polyimides and a va riety of other polymeric hosts has been investigated. The chromophores are aligned using electric field poling and second-harmonic generatio n (SHG) is used to probe the decay of the electric field poling induce d alignment. The decay rate of the SHG signal from films poled using b oth a corona discharge and side-by-side in-plane electrodes was measur ed. When electrodes are chosen so that the effects of charge injection are minimized, little difference has been observed between the orient ational decays from films poled using the two methods for either an am orphous preimidized polyimide host or a highly anisotropic film poled during imidization. The films imidized during poling showed significan t orientational stability at 250-degrees-C for over 15 h after a fast initial partial decay. In addition, the decay of the SHG signal was me asured as a function of temperature below the glass transition in a wi de variety of different polymer host systems. The temperature dependen ce of the decay was found to be non-Arrhenius, but could be strongly c orrelated with the glass transition temperature of the guest-host syst em using an empirical relationship similar to the Williams-Landel-Ferr y or Vogel-Tamann-Fulcher equation.